Changes of perivascular macrophages in the process of brain edema induced by cold injury.

Perivascular macrophages are considered as cerebral scavenger cells under physical and pathological conditions. In this study, we tried to examine changes of perivascular macrophages, especially changes of the characteristic lysosomal inclusion bodies that are rich in hydrolytic enzymes, in the process of brain edema induced by cold injury. Wistar male rats aged 4 months were treated with dry ice for 20 minutes through a drilled hole at the parietal bone. At different time points after the cold injury, cerebral cortex was excised and the immunoreaction for cathepsin D, one kind of lysosomal protease, was examined by post-embedding immuno-electron microscopy. The reactions of cathepsin D were located in the inclusion bodies of perivascular macrophages. At 5 and 10 hours after cold injury, the reactions increased dramatically. Then the reactions inclined to decrease, and reached the minimum at 1 week after cold injury. The reactions seemed to recover at 2 weeks after cold injury. The changes of cathepsin D reactions suggest that the function of perivascular macrophages as scavenger cells were activated in the early phase of the process of brain edema, their later declines might be caused by severe pathological conditions.